144 On the Tarsus and Carjpus of Birds. 



Knowing the importance of making many observations 

 upon different species, in order to arrive at any general 

 truth in the matter, I studied the embryos of all the birds at 

 my limited command, and my only regret is, that the species 

 I was able to examine were so few in number, and so 

 similar in character. For this material my thanks are 

 chiefly due to Mr. Frank L. Scribner and Anson Allen, Esq. 



The embryos studied were those of the Bank swal- 

 low, Cotyle riparia; Eave swallow, Hirundo lunifrons; 

 Kingbird, Tyrannies Carolinensis; Crow blackbird, Quis- 

 calns versicolor; Cow blackbird, Molot/irus j^ecoris; Blue- 

 bird, jSialia sialis; Chipping sparrow, Spizella socialis; 

 Yellow warbler, Dendroeca cestiva; Wilson's thrush, Turdus 

 fuscescens, and the Spotted sandpiper, Tringoides macula- 

 rius. 



I have no means of determining, with certainty, the age 

 of any of the embryos examined, but have made a careful 

 life-size drawing of each one, so that an approximate idea 

 may be formed of their condition and age. 



As all these studies were made from living specimens, 

 more dependence can be placed upon the results obtained, 

 than if they had been drawn from alcoholic specimens, in 

 which the tissues are opaque. 



Tarsus. (See plate iv.). In all the embryos ex- 

 amined, there Avere three distinct bones composing the 

 tarsus. Two of these belonged to the proximal series, one 

 corresponding to the tibia, and the other to the fibula, rep- 

 resenting, respectively, the astragalus and calcaneum. (It 

 seems better to use the terms given by Gegenbaur to these 

 bones, as it removes all objection on the score of question- 

 able homologies. The terms iihiale and fihidare will there- 

 fore be applied to these two boues, and centrale to the 

 remaining one belonging to the distal series.) The tihiale 

 is generall}^ the largest, and in birds, the inner condyle at 

 the distill end of the tibia is usually the largest, which is 

 in accordance with the proportions of the tarsal bone repre- 



